1. Field of the Invention
Exemplary aspects of the present invention generally relate to a sheet cutting device that cuts a sheet roll to desired length, and more particularly to a sheet cutting device installed in an image forming apparatus such as a printer, copier, or facsimile machine.
2. Description of the Related Art
Image forming apparatuses are known that feed a sheet of recording media such as paper or the like from a sheet roll, constituted as one long continuous sheet wound around a core, in a predetermined sheet conveyance direction to form an image on the sheet. Such image forming apparatuses generally include a sheet cutting device that cuts the sheet roll to a predetermined length using a cutter traveling laterally in a sheet width direction that is perpendicular to the sheet conveyance direction.
After cutting the sheet roll while moving outward, a cutter unit that holds the cutter therein is moved homeward and returned to its home position to be ready for the next cutting operation. At this time, use of a single path for both outward and homeward movement of the cutter unit may cause cutter jam, in which a sheet that has been already cut from the sheet roll contacts the cutter during the homeward movement of the cutter unit and thus hinders the movement of the cutter unit.
In order to prevent cutter jam, there is known an image forming apparatus including a sheet cutting device in which two separate paths are provided for outward and homeward movement of the cutter unit, respectively. In such a sheet cutting device, a homeward path of the cutter is provided downstream from an outward path thereof in the sheet conveyance direction. After cutting the sheet roll during the outward movement, the cutter travels back to its home position through the homeward path positioned downstream from a new or subsequent leading edge of the sheet roll.
However, in the above-described image forming apparatus, a carriage mounting a recording head thereon and the cutter unit are individually provided side by side in the sheet conveyance direction, resulting in an increase in the size of the image forming apparatus in the sheet conveyance direction. In addition, although the cutter is moved outward and homeward through the two different paths, respectively, the cutter unit itself is still positioned on a sheet conveyance path in order to prevent contact between the sheet that has been already cut and the cutter during the homeward movement. Consequently, the next sheet cannot be conveyed from the sheet roll until the cutter and the cutter unit are returned to the home position, thereby reducing productivity.
In another approach, the carriage and the cutter unit are disposed one above the other in a sheet thickness direction to reduce the size of the image forming apparatus in the sheet conveyance direction. In addition, compared to the outward path of the cutter unit, the homeward path thereof is retracted from the sheet conveyance path in the sheet thickness direction so that the cutter unit after cutting of the sheet roll is movable homeward while being retracted from the sheet conveyance path.
In the above-described configuration, a cutter casing that accommodates the cutter is pulled in the sheet width direction by a movable member to cut a sheet from the sheet roll. After cutting of the sheet roll, the cutter casing is rotated relative to the movable member to retract the cutter unit from the sheet conveyance path. However, any clearance, or parts tolerance, between a rotary shaft of the cutter casing and a bearing hole of the rotary shaft or slight movement of the cutter casing relative to the rotary shaft in a thrust direction may displace the cutter casing during cutting of the sheet roll due to cutting load, resulting in improper cutting of the sheet roll.
One conceivable way to prevent the displacement of the cutter casing during the cutting of the sheet roll is to reduce the clearance between the rotary shaft of the cutter casing and the bearing hole of the rotary shaft to fix the relative positions of the cutter casing and the rotary shaft. However, firm fixing of the relative positions of the cutter casing and the rotary shaft increases the load during rotation of the cutter casing.